1 files changed, 77 insertions, 0 deletions
diff --git a/rand/rand_jitter/src/error.rs b/rand/rand_jitter/src/error.rs
new file mode 100644
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+++ b/rand/rand_jitter/src/error.rs
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+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use rand_core::Error;
+use core::fmt;
+
+/// Base code for all `JitterRng` errors
+const ERROR_BASE: u32 = 0xAE53_0400;
+
+/// An error that can occur when [`JitterRng::test_timer`] fails.
+/// 
+/// All variants have a value of 0xAE530400 = 2924676096 plus a small
+/// increment (1 through 5).
+///
+/// [`JitterRng::test_timer`]: crate::JitterRng::test_timer
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[repr(u32)]
+pub enum TimerError {
+    /// No timer available.
+    NoTimer = ERROR_BASE + 1,
+    /// Timer too coarse to use as an entropy source.
+    CoarseTimer = ERROR_BASE + 2,
+    /// Timer is not monotonically increasing.
+    NotMonotonic = ERROR_BASE + 3,
+    /// Variations of deltas of time too small.
+    TinyVariantions = ERROR_BASE + 4,
+    /// Too many stuck results (indicating no added entropy).
+    TooManyStuck = ERROR_BASE + 5,
+    #[doc(hidden)]
+    __Nonexhaustive,
+}
+
+impl TimerError {
+    fn description(&self) -> &'static str {
+        match *self {
+            TimerError::NoTimer => "no timer available",
+            TimerError::CoarseTimer => "coarse timer",
+            TimerError::NotMonotonic => "timer not monotonic",
+            TimerError::TinyVariantions => "time delta variations too small",
+            TimerError::TooManyStuck => "too many stuck results",
+            TimerError::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
+
+impl fmt::Display for TimerError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.description())
+    }
+}
+
+#[cfg(feature = "std")]
+impl ::std::error::Error for TimerError {
+    fn description(&self) -> &str {
+        self.description()
+    }
+}
+
+impl From<TimerError> for Error {
+    fn from(err: TimerError) -> Error {
+        // Timer check is already quite permissive of failures so we don't
+        // expect false-positive failures, i.e. any error is irrecoverable.
+        #[cfg(feature = "std")] {
+            Error::new(err)
+        }
+        #[cfg(not(feature = "std"))] {
+            Error::from(core::num::NonZeroU32::new(err as u32).unwrap())
+        }
+    }
+}
+